/**
 * 共享相机 composable (H5 only)
 *
 * 用法: const { captured, errorMsg, startCamera, flipCamera, takePhoto, retake, confirm } = useCamera('my-video-id')
 *
 * - 自动在 onMounted 启动摄像头
 * - 自动在 onBeforeUnmount 停止摄像头
 * - 返回 ref 和方法,业务页只需负责 UI 布局
 */
import { ref, onMounted, onBeforeUnmount } from 'vue'
import { openCamera, stopCamera, captureFrame, describeCameraError, type Facing } from '@/utils/camera'

export function useCamera(videoId: string) {
	const facing = ref<Facing>('environment')
	const captured = ref<string>('')
	const errorMsg = ref<string>('')

	function getVideoEl(): HTMLVideoElement | null {
		return document.getElementById(videoId) as HTMLVideoElement | null
	}

	async function startCamera() {
		errorMsg.value = ''
		const video = getVideoEl()
		if (!video) {
			errorMsg.value = '视频元素未找到'
			return
		}
		try {
			await openCamera(video, facing.value)
		} catch (err) {
			errorMsg.value = describeCameraError(err)
			console.error('[camera]', err)
		}
	}

	function flipCamera() {
		facing.value = facing.value === 'environment' ? 'user' : 'environment'
		startCamera()
	}

	async function takePhoto() {
		const video = getVideoEl()
		if (!video) return
		try {
			captured.value = captureFrame(video)
		} catch (err) {
			uni.showToast({
				title: (err as Error).message || '截图失败',
				icon: 'none',
			})
		}
	}

	function retake() {
		captured.value = ''
	}

	async function confirm() {
		// POC: 假上传 + loading 给用户完整仪式感
		uni.showLoading({ title: '上传中...' })
		await new Promise<void>((resolve) => setTimeout(resolve, 800))
		uni.hideLoading()
		uni.showToast({
			title: '已保存 (POC 未上传)',
			icon: 'none',
			duration: 1500,
		})
		captured.value = ''
	}

	onMounted(() => {
		startCamera()
	})

	onBeforeUnmount(() => {
		const video = getVideoEl()
		if (video) {
			stopCamera(video)
		}
	})

	return {
		facing,
		captured,
		errorMsg,
		startCamera,
		flipCamera,
		takePhoto,
		retake,
		confirm,
	}
}